Quote from: Stephen on January 29, 2012, 08:13:51 PM
Sorry, the last post was not clear. The phone being used is solid, high quality - 18 years old and the best audio of any phone I've ever used. The phone is not the problem.
IMO, that's not obvious. Some phones are sensitive to common-mode AC voltage on the line; the new router may have more leakage, which is being conducted over the Ethernet cable.
If this is the case, you will hear the hum, even when there is no VoIP. Pick up the phone, hear dial tone and press one digit to stop the dial tone. Do you hear hum? If so, does it get louder if you grasp the coiled handset cord with your hand? If so, that's likely the problem.
If the above is your issue, possible fixes: If the power plug for the new router is not polarized and does not have a ground pin, try plugging it in "upside down" (with the plug blades swapped). If no luck, try connecting the old router behind the new (OBi to LAN port on old router, WAN port of old router to LAN port of new router, WAN port of new router to modem). The old router must be set for DHCP addressing. Or, if you have an old Ethernet switch or hub, try connecting it between OBi and new router. If none of this helps, please post make and model of both routers.